Dyne, Sarepta shares tumble as Novartis setback weighs on muscle disease drug developers

Pfizer

08/09/2026 18:00

By Sriparna Roy
Sept 8 (Reuters) - Shares of Dyne Therapeutics DYN.O and Sarepta SRPT.O slumped on Tuesday after Novartis' NOVN.S treatment for a muscle-wasting disorder failed in a trial, fueling investor concerns about the prospects of similar therapies for the tough-to-treat rare disease.
Dyne's stock led declines among companies developing a treatment for myotonic dystrophy type 1, tumbling nearly 18%. Shares of Sarepta and PepGen PEPG.O fell more than 9% and 5%, respectively. Novartis' shares closed 10.9% lower on the Swiss exchange on Tuesday.
The genetic disorder, which causes progressive muscle weakness and delayed muscle relaxation known as myotonia, has no approved treatments. Drug development for it has been challenging, with several companies, including Biogen BIIB.O, abandoning or shelving their programs over the past decade.
 "This definitely increases the risk for the space, and it's a disappointment, a $12 billion disappointment," Oppenheimer analyst Kostas Biliouris said.
Novartis acquired the drug through its $12-billion acquisition of Avidity.
     
The failure was particularly concerning for Dyne as its trial, like Novartis', uses video hand opening time - how quickly a patient's hand relaxes after squeezing - as a key trial goal for its candidate, DYNE-101.
 "The (Novartis) failure makes Dyne's own trial much more risky," Cantor Fitzgerald analyst Eric Schmidt said.
Novartis said late-stage trial data showed its drug, del-desiran, failed to show a statistically significant improvement over placebo on video hand opening time. 
The Swiss company did not disclose numerical results, saying that it is evaluating the full dataset and will engage with health authorities to determine the most appropriate development path for the drug.
"The big question is whether it's an endpoint miss or... whether mechanism has completely failed or not," said H.C. Wainwright analyst Ananda Ghosh.
Dyne plans to present additional one-year data at conferences this month.
Sarepta is evaluating an investigational small interfering RNA therapy called SRP-1003 in early stage trial for type 1 myotonic dystrophy.
        
     

 (Reporting by Sriparna Roy in Bengaluru; Editing by Leroy Leo)
 ((Sriparna.Roy@thomsonreuters.com;))